Promoters contain specific DNA sequences and response elements that provide a secure initial binding site for RNA polymerase and for proteins called transcription factors that recruit RNA polymerase. These transcription factors have specific activator or repressor sequences of corresponding nucleotides that attach to specific promoters and regulate gene expression.
Promoters used in biotechnology are of different types according to the intended type of control of gene expression. An extensive number of plant promoters, are reported in the literature. These plant promoters act as useful tools for expressing proteins or peptides in transgenic plants or plant cells or alternatively for silencing genes or gene families. Promoters are generally grouped into following categories namely: constitutive promoters, inducible promoters, developmentally regulated promoters, and tissue specific promoters.
Constitutive promoters direct expression in virtually all the tissues and are largely independent of environmental and developmental factors. As their expression is normally not conditioned by endogenous factors, constitutive promoters are usually active across species and even across kingdoms.
Numerous promoters that function in plant cells are known in the art and are available for use in recombinant polynucleotides for expression of desired genes in transgenic plant cells.
U.S. Pat. No. 5,510,474 describes a maize ubiquitin promoter; U.S. Pat. No. 5,850,018 describes a maize ZMDJ1 promoter/leader sequence, and US 20110167518 describes a maize sark promoter.
Viral promoters capable of infecting plants are less preferred for the transformation of host plant species, as infection of the plants with the virus may cause silencing of the transgene (Seemanpillai et al., 2003, MoI Plant Microbe Interact. 16(5): 429-438; Al-KafFef al, 2000, Nat Biotechnol. 18: 995-9).
Currently commonly used constitutive promoter is the 35S promoters or enhanced 35S promoters (the “35S promoters”) of the cauliflower mosaic virus (CaMV) of isolates CM 1841 (Gardner et al., 1981, Nucleic Acids Research 9, 2871-2887) CabbB-S (Franck et al, 1980, Cell 21, 285-294) and CabbB-JI (Hull and Howell, 1978, Virology 86, 482-493); the 35S promoter described by Odell et al (1985, Nature 313, 810-812).
WO2007069894 describes that the activity of the CaMV35S promoter in transgenic plants was sensitive to abiotic stress, especially heat stress caused when the transgenic plants were grown in the field in Spain.
There is a need for development of different constitutive plant promoters for gene stacking approaches, as the use of several identical promoters may result in gene silencing (Yang et al., 2005, Plant Mol Biol. 58: 351-366).
Isolation and functional characterization of a cotton ubiquitination-related promoter and 5′UTR that drives high levels of expression in root and flower tissues has already been described. uceA1.7 is a strong constitutive regulatory sequence composed of a promoter (uceApro2) and its 5′UTR is useful in genetic transformation of dicots, having high potential to drive high levels of transgene expression in crops, particularly for traits desirable in flower and root tissues (Viana et al., 2011, BMC Biotechnology, 11:115). Promoters from cotton specific to green tissues, flower buds-inflorescences (with lower activity in vegetative tissues), seed and fiber are disclosed in the prior arts
It is desirable from a regulatory point of view to use promoters derived from plants in the generation of transgenic plants. Therefore, new constitutive promoters of plant origin are required, which regulate transgene expression positively in response to adverse environmental stress. This will directly help in the field of plant biotechnology to improve crop yields for assurance of global food security.